New California Pest Quarantine Areas Declared

New detections of two pests – the European Grapevine Moth (EGVM) in the Lodi area and invasive melon fruit flies near Bakersfield – have caused the California Department of Food and Agriculture (CDFA) to declare new pest quarantine areas. The EGVM finds have led to an extension of the quarantine for the pest to San Joaquin County. Ninety-six square miles are now under quarantine there, bringing the total area under quarantine statewide to 1,995 square miles. To see a map of this quarantine area, or any other in the state, visit www.cdfa.ca.gov.

The quarantine primarily affects growers as well as those who harvest, transport and otherwise process or handle crops. These business people generally sign compliance agreements that indicate how crops, vehicles, equipment and related articles are to be treated during the quarantine.

Residents are also affected by the quarantine. Those who have grapes, stone fruit trees (peaches, plums, etc.) and other “host plants” for this pest in their yards are asked to harvest and consume their fruit on-site to further limit the risk of spreading the pest.

EGVM, or Lobesia botrana, is found in southern Asia, Japan, Europe, North Africa, Anatolia, the Caucasus and in South America. The pest primarily damages grapes, but has also been known to feed on other crops and plants.

The EGVM larvae, not the adult moths, are responsible for the damage to grapes. Larvae that emerge early in the spring feed on grape bud clusters or flowers and spin webbing around them before pupating inside the web or under a rolled leaf. If heavy flower damage occurs during this first generation, the affected flowers will fail to develop and yield will be reduced.

Second-generation larvae enter the grapes to feed before pupating in the clusters or in leaves. Larvae of the third generation – the most damaging – feed on multiple ripening grapes and expose them to further damage from fungal development and rot. These larvae overwinter as pupae in protected areas such as under bark, and emerge as adults the following spring.

The second quarantine announced Thursday measures 82 square miles and is in place in Kern County, where invasive melon fruit flies have been detected in the Arvin/Mettler area.

The movement of host fruits and plants grown in the quarantine areas is restricted. Residents living within the boundaries are asked not to move host plants and materials from their property.

“We don’t see the melon fruit fly in California as often as some as some other pests, but it is still very damaging,” said CDFA Secretary A.G. Kawamura. “This quarantine allows us to protect surrounding uninfested areas by preventing movement of the fruit fly.”

While fruit flies and other pests threaten California’s crops, the vast majority of them are detected in urban and suburban areas. The most common pathway for these pests to enter the state is by “hitchhiking” in fruits and vegetables brought back illegally by travelers as they return from infested regions around the world.

The melon fly is native to Asia. The melon fly occurs in Africa, Sri Lanka, China, Guam, India, New Guinea, Taiwan, Rota, the Ryukyu Islands, Thailand and much of Southeast Asia. In the United States, its distribution is limited to the Hawaiian Islands. The larvae of the melon fly have been recorded in over 100 different hosts worldwide. It is a particularly serious pest of melon and cucumber-type crops.

A female melon fly lays eggs under the skin of host fruit. These eggs hatch into larvae, or maggots, which tunnel through the flesh of the fruit or other plant parts, leaving the interior of the fruit a rotten mass and making it unfit for consumption.

Treatment of the melon fruit fly relies upon trapping. Fly lure is placed in a trap that attracts and eradicates the insects. Treatment in Kern County is already underway.

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